/** * Returns the identifier in the form {@code <SCHEME>~<VALUE>~S~<VALID_FROM>~E~<VALID_TO>}. * * @return the identifier, not null */ @Override public String toString() { StringBuilder buf = new StringBuilder(_identifier.toString()); if (_validFrom != null) { buf.append("~S~").append(_validFrom.toString()); } if (_validTo != null) { buf.append("~E~").append(_validTo.toString()); } return buf.toString(); }